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AR# 35522

Virtex-5 GTP - PLL_DIVSEL_FB=3 is not allowed


In the RocketIO Virtex-5 GTP Wizard v2.0 and later, some configurations are not allowed.

For example, in RocketIO GTP Wizard v1.10 I could choose a 125Mhz reference clock when the linerate is 3.75 Gbps.

However, in RocketIO GTP Wizard v2.0 a 125Mhz reference clock is no longer selectable in the GUI when linerate is 3.75 Gbps.

Why has this changed?


GTP performance has not yet been fully characterized when PLL_DIVSEL_FB=3.

It is not recommended to set PLL_DIVSEL_FB to 3.

AR# 35522
Date Created 05/03/2010
Last Updated 10/09/2014
Status Active
Type General Article
  • Virtex-5 LXT
  • Virtex-5 SXT